Most automotive vehicles have a roof. The roof of the automotive vehicle is typically joined to the remainder of the car body by at least a pair of transversely-spaced front and rear pillars. The front pillar which is adjacent to the windshield is referred to as the A pillar. The rear pillar, which is adjacent to the rear window opening, is typically referred to as the C pillar. The C pillar's outer body is formed from two large sheet metal stampings. The first stamping is the roof panel and the second stamping is a rear quarter panel. The roof panel has an integral portion forming a depression for placement of the rear glass window pane and for forming an upper portion of the C pillar. The roof panel portion of the C pillar is typically placed in an over-lapping manner in connection with the C pillar portion of the rear quarter panel. The rear quarter panel also has a depression for the rear window pane. The rear quarter panel additionally forms the rear door opening and the rear side panel of the vehicle.
The two body panels of the C pillar are fitted and welded together. The C pillar can have an irregular surface appearance at the seam line due to gaps in fit up and/or distortion from the heat of the welding. For aesthetic reasons, it is typically desired that the C pillar appear to be one continuously-formed piece of sheet metal. To cover up the seam overlap, head distortion and/or gaps in fit up between the roof panel C pillar portion and the quarter panel C pillar portion, brazing is typically applied. After the brazing solidifies, a grinder is applied to smooth out the brazing to provide a smooth transition between the sheet metal of the C pillar which is integral with the roof panel and the sheet metal which is integral with the rear quarter panel. After the grinding operation and subsequent painting of the vehicle, the seam line between the two sheet metal portions of the C pillar becomes virtually indistinguishable.
In the most recent two decades efforts have been made to utilize robots to perform the brazing operation (sometimes referred to as soldering). A device, typically referred to as a brazing nozzle, is utilized to project liquefied silicon brazing material onto the C pillar. On most vehicles, the C pillar has surface curvatures in the fore and aft direction, in the transverse direction and in the vertical direction of the vehicle. Accordingly, the brazing nozzle at the end of the robot must follow a complex multi-dimensional path and should be maintained at a perpendicular orientation with respect to the surface of the C pillar. Additionally, the brazing nozzle should be positioned at a constant distance from the surface of the C pillar to provide an even disposition of brazing and to prevent excessive heat transfer to the C pillar which could inadvertently warp or damage the sheet metal of the C pillar. Empirical experience has shown that the complex geometrical shapes of the C pillar make a purely mathematical modeling of the path of the robot to be unworkable. Accordingly, a teach tool is utilized to program the robot. When using a teach tool an operator will physically manipulate the robot in the desired path of operation. The motion imparted to the robot will be transferred to its controller and the robot will "memorize" the path followed by the teach tool. Thereafter the robot can repeatedly follow the prescribed path.
Prior to the present invention, a rod-like pointer was used as the teach tool for the robot. When using a rod pointer to teach the robot, sometimes the operator inadvertently would not have the pointer perpendicular to the instant surface of the C pillar, which resulted in several problems when the robot was using the brazing nozzle to braze the C pillar. Whenever the pointer was not perpendicular to the surface, the distance from the brazing nozzle to the surface of the C pillar would not be constant. A non-constant distance causes the brazing to be misapplied and can sometimes inadvertently cause the sheet metal of the C pillar to be overexposed to heat and accordingly warp or bend. To compensate for the lack of constant distance, typically an excess amount of brazing was applied. The excess amount of brazing was undesirable because additional brazing time caused an increase in production time, which mandated additional production time for the grinding operation to smooth out the brazing.
It is desirable to provide a method of robotically brazing a resetting multi-dimensional panel seam line on a resetting automotive body C pillar while at the same time keeping a brazing nozzle at a constant angle with respect to the C pillar. It is desirable to provide a method of robotically brazing a resetting multi-dimensional panel seam line on a resetting automotive body C pillar while at the same time keeping a brazing nozzle at a constant distance away from the surface of the C pillar.